How can I instant delete all of the actions ?
Every animation that is not used by any object and that is not F (fake user, which means that doesn't need to have any user to be saved) won't be saved when you'll close and reopen your file.

Now, to delete an action that is currently used, go in the Dopesheet / Action Editor mode, and press shift and the X on the right of the name of the animation. When you'll reopen the file the animation won't be here anymore.

To delete a F (fake user) animation, disable the F, and same thing: press shift and the X and reopen the file.

If an animation isn't assigned to any object anymore, you can go to the Outliner, select Orphan Data in the dropdown menu, you'll see all the orphan animations, select them all and right click > Delete. Even the F animations will be deleted.

If you only want to delete the visible animations, you can select all your objects, press the Spacebar and type "Remove Animation", You can also go into the Outliner, type "Animation" in the Search box, select all the animations and right click > Clear Animation Data.